1. Field of the Invention
The present invention relates to a motor for linear compressors that is capable of generating a driving force, by means of which a piston is linearly reciprocated in a cylinder, and more particularly to an outer stator for such linear compressor motors wherein a coil assembly of the outer stator and core blocks of the outer stator, which together constitute the motor, are integrated, whereby the outer stator is securely and reliably assembled in the linear compressor.
2. Description of the Related Art
Generally, a linear compressor is constructed such that a linear driving force from a motor is transmitted to a piston, which is linearly reciprocated in a cylinder, whereby a coolant gas is introduced, compressed, and discharged.
FIG. 1 is a cross-sectional view showing a conventional linear compressor, FIG. 2 is a perspective view showing an outer stator for linear compressor motors according to the prior art, and FIG. 3 is a cross-sectional view taken along the line A—A of FIG. 2.
As shown in FIG. 1, the conventional linear compressor comprises: a hermetically sealed container 1; a cylinder block 4 and a back cover 5 mounted in the hermetically sealed container 1 such that shock applied to the cylinder block 4 is absorbed by means of a damper 2 and shock applied to the back cover 5 is absorbed by means of another damper 3; a cylinder 6 fixedly attached to the cylinder block 4; a piston 7 disposed in the cylinder 6 such that the piston 7 is linearly reciprocated in the cylinder 6; a magnet frame 8 fixed to the piston 7; and a motor M for linearly moving the piston 7.
The motor M comprises: an outer stator 10 dispose between the cylinder block 4 and the back cover 5; an inner stator 20 disposed inside the outer stator 10 while being spaced apart from the outer stator 10; and a magnet 30 disposed between the outer stator 10 and the inner stator 20. The magnet 30 is fixed to the magnet frame 8.
The outer stator 10 comprises: a coil assembly 13 comprising a bobbin 11 and a coil 12 wound on the bobbin; and left-side and right-side core blocks 14 each made of a plurality of laminated steel plates and assembled with the coil assembly 13 such that the core blocks 14 surround the coil assembly 13. The core blocks 14 are arranged in large numbers while being spaced apart from each other by a prescribed distance in the radial direction on the bobbin 11.
In the linear compressor with the above-stated construction, an electro-magnetic field generated between the outer stator 10 and the inner stator 20 is varied when alternating current is applied to the coil 12 of the outer stator 10. As a result, the magnet 30 is linearly reciprocated, and thus the magnet frame 8 and the piston 7 are also linearly reciprocated. Consequently, a coolant gas is introduced into a compression chamber C through an inlet pipe 41 and an inlet channel 42, and is then compressed. The compressed coolant gas is discharged to the outside through an outlet pipe 43.
The structure and production process of the outer stator 10 of the motor M will now be described in more detail with reference to FIGS. 2 and 3.
On the bobbin 11 with flange parts 11a formed at both sides thereof while being extended in the radial direction is wound the coil 12 so that the coil assembly 13 is prepared. The core blocks 14, each of which is made of a plurality of laminated steel plates, are arranged in large numbers while being spaced apart from each other in the radial direction so that the core blocks 14 surround the coil assembly 13.
While the coil assembly 13 is assembled with the core blocks 14, the coil assembly 13 and the core blocks 14 are put in an over mold (not shown), and a synthetic resin is injected into the over mold so that an insulating layer 16 is formed between the coil 12 of the coil assembly and the core blocks 14, and over mold layer 17 on the outer circumferences of the coil assembly 13 and the left-side and right-side core blocks 14. After the outer stator 10 is manufactured as described above, the outer stator 10 is disposed between the cylinder block 4 and the back cover 5, as shown in FIG. 1, and the outer surfaces of the core blocks 14 are pressed against the cylinder block 4 and the back cover 5 by means of a plurality of bolt and nut assemblies 9. Finally, the outer stator 10 is assembled in the linear compressor.
In the outer stator 10 for linear compressor motors according to the prior art, a high-temperature synthetic resin is injected so that the over mold layer 17 is formed, which is required to integrally fix the core blocks 14 and the coil assembly 13 to each other. Consequently, the core blocks 14 may be thermally deformed, by which design dimensions are changed. Furthermore, the over mold and the synthetic resin are necessary, which increases the production cost of the outer stator 10 of linear compressor motors.
Only the core blocks 14 of the outer stator 10 are pressed between the cylinder block 4 and the back cover 5 by means of the bolt and nut assemblies 9, which are then assembled in the linear compressor. Consequently, there may occur relative movement between the bobbin 11 and the core blocks 14 or the coil 12 wound on the bobbin may be slightly shifted due to vibration or shock generated when the linear compressor is operated or due to inferiority of the over mold layer 17.